The history behind a rare astronomical event: The transit of Venus

June 1, 2012

June 1, 2012 Doug Duncan

A very unique and rare astronomical event is going to take place June 5. It’s called the Transit of Venus. On that day Venus passes between the Sun and Earth giving people a chance to see the planet against the backdrop of the solar disc, something that won’t happen again for 121 years.

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The history behind a rare astronomical event: The transit of Venus

A very unique and rare astronomical event is going to take place June 5. It’s called the Transit of Venus. On that day Venus passes between the Sun and Earth giving people a chance to see the planet against the backdrop of the solar disc, something that won’t happen again for 121 years.

CUT 1 “It’s incredibly rare and it’s incredibly fun. You’re seeing something that very few people will ever get to see. Kind of like when I saw Halley’s comet. Halley’s comet is not the brightest comet that there is but it’s really cool because you can only see it once in a lifetime.” (:17)

That is Doug Duncan, director of CU’s Fiske Planetarium and a senior instructor of astrophysics and planetary sciences at CU-Boulder. He says the event is not only rare but it has a very important historical significance as well.

CUT 2 “The reason the transit was important in the past is that if you look at Venus going in front of the sun from two different places on the Earth, you can use geometry and you can figure out how far away Venus is and that was the first time we knew the size of the solar system. (:19)

Duncan says it was Edmund Halley, of Halley’s comet fame, that figured this out in the in the late1600s. But it took until the transit in 1761 for astronomers to prove his theory was right.

CUT 3 “Edmund Halley figured out that if you could look at Venus moving in front of the sun it would look different from two different vantage points. (:07) It’s like when you are driving on any highway the trees and fences that are close to you seem to move fast and the mountains that are further away seem to move slower. (:16) So if you measure how fast something shifts, or how much it shifts from two different places on the Earth, you can, if you’re clever with geometry, figure out how far away they are. The first time we knew the size of our solar system was 1761 and 1769.” (:32)

To observe the transit, Duncan says you need to get special dark, sun watching glasses. He says do not under any circumstances look at the sun directly unless you have these glasses.

CUT 4 “You have to be very careful if you look at the sun. The sun is so bright that you can’t look at it without protecting your eyes with very, very dark glasses. Not sun glasses but dark glasses. (:11) Sun watching glasses are a thousand times darker than ordinary sunglasses. The company that makes them calls them the Eclipse Shades. We call them eclipse-watching glasses.” (:26)

If you can’t get the dark glasses Duncan says you can still watch the transit by going to the Fiske Planetarium web site at http://fiske.colorado.edu. He says they will post a live image of the transit using a solar telescope at CU’s Bausch-Somers Observatory. For most people in North America the transit will begin late afternoon.